[cruella89deville]

Hey ladies and gents.

I have a '89 Sedan Deville with the 4.5. Ever since I got it, it'd have the high initial idle thing that we all have. it'll also speed u prandomly as well. I'll go through a full breakdown of what it does so that I'll know exactly what to fix so it doesn't cost me a billion dollars. lol.

When I got to turn on the car, sometimes the pedal will pulste it's self as if it's trying to prime a carbeurator. It's obviously FI though. When it does this, the idle will skyrocket. Every once in a while it'll be fine, but usually it goes nuts. Every slight once in a while it'll even NOT come back to normal. It'll just keep revving. Often after I turn it off and turn it back on after that it'll do it again. Vary rarely, it'll also speed up greatly WHILE I'm driving. Like yesterday, I was driving along like normally through my neighborhood when suddenly the car frantically speeds up. When I come to a stop finally (my front brakes need changed) I can hear the engine still high revving and trying to move the car forward more. When I let off the brake the car propulses it's self forward greatly. I live on the top of a hill and I never touched the gas once. It got me up the hill. haha!! Then when it realises what it's doing, it'll dramatically reduce revs after it goes BWAAAAAA like the engine ran out of breath. Other times, however, the car is perfectly fine.

What sensor is it? Can I fix it myself?

Thanks!!!

:want:4.5

 

[Kev]

I also have a 89 DeVille, I would start first with a few basics unless you've done this already.

1. Throttle body cleaning. Clean the throttle body as described in numerous other threads, you can do a search to find the info. Be sure to disconnect the neg battery cable for 1 minute to initiate the idle re-learn function in the ECM.

2. Check and clean the EGR valve. There are also other threads describing what to do here.

3. Check for error codes. Press and hold 'Off' and Warmer' together until the car goes into it's self diagnostics mode. Watch your dash and be ready to write down any error codes, it should read 7.0 when it is finished.

By the way, when was the last time it was tuned, i.e. new plugs, plug wires, cap & rotor, etc.?

Also, do a close visual inspection of all your wires, connectors and hoses for leaks, frays, loose connections etc.

 

[Cadillac_Rancher]

Sounds like a bad/failing ISC. When they go bad you tend to hear them click click click when you shut the car off, this is the sound of the gears in it jumping teeth. The pulsating in your peadal is probably being pushed then let go when the ISC hits its bad tooth and the tension of the throttle body pushes its plunger down again. So its probably holding it high realizing that where it should be has a bad tooth and will fall. then it realizes thats tooo high, then it drops below the bad tooth and its too low. Of course ensure your regular maintainence is good clean TB and EGR then replace and Re-Learn ISC.


-The Cadillac Rancher

 

[cruella89deville]

I cleaned those items first, before anything else.

How much is an ISC, where do I get it, and can I install it myself? lol.

 

[Cadillac_Rancher]

I cleaned those items first, before anything else.

How much is an ISC, where do I get it, and can I install it myself? lol.

Um its not too much, but not too little either. Get it at any parts store..easy to install, but you must do the re-learn proceedure, so do a search for it and then do that affter you the install but that should fix it.

-The Cadillac Rancher

 

[cruella89deville]

See...like today. It ran fine. The only problem was that when you're at very little throttle it like bogs a little or hesitates. It's hard to explain. Hesitates is probably the best. I've got some cash finally...so I might go hit that up tomorrow.